Some of imaging devices of an electronic camera and so forth detect a shake state of a camera body (housing) to perform correction for counteracting a shake thereof. In particular, it is general to perform optical shake correction in which a taking lens and an image sensor are moved so as to counteract the shake, such as described in Japanese Patent Laid-Open Publication Nos. 5-249529, 5-137048 and 2000-221039 for instance.
In a camera provided with such an optical shake-correction function, angular information of the shake is produced by time integration of angular velocity detected from a shake detector detecting the shake of the camera body. A lens drive signal is outputted in accordance with the angular information to move a correction lens. By virtue of this, an imaging optical axis is deflected to offset the shake.
By the way, the above-described shake detector is generally provided with an angular-velocity sensor of a gyro sensor and so forth. This kind of the angular-velocity sensor converts a force of mechanical torsion into an electromotive force by a piezoelectric element to perform the detection. Consequently, an output level is small and error is likely to be caused due to increased temperature. Further, since an output signal often includes components of offset and drift, detection accuracy deteriorates depending on usage environment. In consideration of this, the electronic camera described in the above-noted Publication No. 5-249529 performs differential amplification of a reference voltage and an output of a vibration detecting sensor at a power-on time. In accordance with the output for which the differential amplification has been performed, the reference voltage is increased or decreased. In this way, the drift component caused in the vibration detecting sensor at the power-on time is removed.
Meanwhile, the camera described in the above-noted Publication No. 5-137048 compares a detection result of the gyro sensor with a predetermined condition. In accordance with a comparison result, a detector including the gyro sensor is initialized. In other words, when a power supply is turned on just after panning and just after largely changing a direction of a tilt or a pan, the detected shake amount becomes an extremely large value because the gyro sensor outputs the shake state of this time. On the other hand, when a temperature changes during usage, a shift of the reference voltage is caused. In such a case an extreme value has been outputted as the shake amount, error detection is prevented by initializing the sensor.
As to an oscillation gyro described in the above-noted Publication No. 2000-221039, the gyro sensor includes an angular velocity sensor, an A/D converter for digitally converting an output of the angular velocity sensor, and a digital signal processor for processing a digital signal outputted from the A/D converter. When the drift is caused on the digital signal based on the output of the angular velocity sensor, the drift component is corrected by an operation performed in the gyro sensor.
However, in the structure of the Publication No. 5-249529, when the camera body is extremely shaken at the power-on time, the reference voltage is changed in accordance with the output of the vibration detecting sensor of that time. Due to this, the shake state is mistakenly detected when the camera body comes to rest. In the structure of the Publication No. 5-137048, when the camera body is slightly shaken in a direction of tilt or pan, initialization is not performed. Due to this, components of offset and drift are added to the output signal for a while. In the structure of the Publication No. 2000-221039, if the drift components are corrected when the body has been changed from the shake state to the still state, a value of the shake state is regarded as a center value and sometimes the still state is mistakenly detected as the shake state.